Led lighting fixture and heat sink therefor

ABSTRACT

A heatsink is formed at least partly from a foamed metal. The heatsink may comprise a plurality of foamed metal plates that are supported in one or more arrays of substantially parallel plates. Curved or helically generated fins are not required. The heatsink may further include a base plate on which the foamed metal plates are supported. A bridge may be mounted to sides of the array of foamed metal plates opposite the base plate to maintain a desired spacing between the foamed metal plates. One or more LEDs may be mounted to a surface of the base plate opposite the foamed metal plates. Reflectors may be mounted to the sides of the LED modules opposite the baseplate of the heatsink to direct the light in an appropriate manner for the desired illumination effect.

This application claims priority on U.S. Provisional Application No.62/015,824 filed on Jun. 23, 2014.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an LED lighting fixture and a heat sink for anLED lighting fixture.

2. Description of the Related Art

A light emitting diode (LED) can provide a bright high quality lightwith a relatively low power input and with a long service life, ascompared to conventional incandescent lights. LEDs also are much smallerthan conventional incandescent lights, and hence potentially can givelighting designers more options for designing an aestheticallyattractive highly functional lighting fixture. However, LEDs generatelarge amounts of heat in a relatively small space. The heat canadversely affect the service life of the LED. The heat generated by anLED lighting system or module must be dissipated for safety reasons andfor UL approval. Metal heatsinks typically are used to draw heat awayfrom the LED and to dissipate the heat into the ambient surroundings.The typical metal heatsink has an array of metal fins that radiate outfrom the LED. The fins provide a large surface area of contact betweenthe heatsink and the ambient air so that heat can be dissipatedefficiently into the air. The things typically define curves to furtherincrease the surface area. These complex heatsink structures normallyare produced by molding or extruding. The molds are complex and costlyand are not redesigned easily to accommodate differences between onelighting fixture and another.

LEDs have received considerable commercial acceptance in environmentswhere a relatively low level of lumens is sufficient. More particularly,an LED that produces a relatively low level of lumens will produceeasily manageable levels of heat and small structures for dissipatingthe heat can be provided easily.

Large public spaces, such as cathedrals, auditoriums, theaters, trainstations and arenas, provide challenges to the designers of lightingfixtures. In this regard, the lighting fixture must provide sufficientlight to a large area and also should be aesthetically attractive to theviewing public. All lighting fixtures must be serviced periodically, andthe design and placement of lighting fixtures should anticipate the needfor periodic access to the lighting fixture for service. Thesignificantly longer service life for an LED makes the LED a desirableoption for a large public space. Additionally, the lower power demandsfor an LED can result in significant savings for illuminating a largepublic space. However, heat dissipation requirements have complicatedefforts to use LED lighting modules or fixtures to illuminate a largepublic space. In this regard, a metal heatsink for an LED lightingfixture that is sufficiently bright to illuminate a large public spacecan be expected to weigh 25 pounds or more. This additional weight cansignificantly complicate efforts to design an aesthetically attractivelighting fixture and to suspend the lighting fixture from a highceiling.

An object of the subject invention is to provide a heatsink that canefficiently dissipate heat from a large LED lighting fixture withoutadversely affecting the weight of the fixture.

A further object of the invention is to provide a lightweight LEDlighting fixture that can efficiently dissipate heat.

Another object of the invention is to provide an LED module with aheatsink that can be incorporated into an existing lighting fixture as areplacement for a less efficient incandescent light.

SUMMARY OF THE INVENTION

The invention relates to a heat sink for an LED lighting fixture or LEDmodule. The heatsink is formed at least partly from a foamed metal, suchas foamed aluminum, a foamed aluminum alloy or foamed copper. The foamedmetal provides a very substantial weight reduction when compared toconventional solid metal heatsinks that are molded or extruded. However,the foamed metal heatsink provides sufficient heat dissipation for anLED lighting fixture even when the LED lighting fixture generatessufficient lumens to light a large space, such as a cathedral,auditorium or theater.

The heatsink may comprise a plurality of foamed metal plates that aresupported in one or more arrays of substantially parallel plates. Curvedor helically generated fins are not required. The heatsink may furtherinclude a base plate on which the foamed metal plates are supported. Abridge may be mounted to sides of the array of foamed metal platesopposite the base plate to maintain a desired spacing between the foamedmetal plates for ensuring an efficient dissipation of heat and formounting a junction box or other such electrical connection.

One or more LEDs may be mounted to a surface of the base plate oppositethe foamed metal plates. Reflectors may be mounted to the sides of theLED modules opposite the baseplate of the heatsink to direct the lightin an appropriate manner for the desired illumination effect.

The heatsinks and the LEDs can be part of a module that can beretrofitted into an existing lighting fixture. This option isparticularly important for older buildings where the aesthetic andcultural appeal of the existing lighting fixture is important.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a lighting fixture inaccordance with an embodiment of the invention.

FIG. 2 is a perspective view of the assembled lighting fixture of FIG. 1including a driver box.

FIG. 3 is a side elevation of view of the assembled lighting fixture ofFIG. L.

FIG. 4 is a top plan view of the lighting fixture.

FIG. 5 is a bottom plan view of the lighting fixture.

FIG. 6 is a perspective view of an alternate heatsink in accordance withthe invention.

FIG. 7 is a side elevational view of the heat sink shown in FIG. 6.

DETAILED DESCRIPTION

A lighting fixture in accordance with the invention is identifiedgenerally by the 10 in FIGS. 1-5. The lighting fixture 10 includes aheat sink 12 formed from a heatsink base 14 and an array of foamed metalplates 16. The heatsink base 14 is substantially circular and has a topsurface 18 and a bottom surface 20. LED fixtures 22 are mounted to thebottom surface 20 of the heatsink base 14. Three LED fixtures 22 areprovided in the illustrated embodiment. However, other arrangements ofthe LED fixtures 22 can be provided in other embodiments. In theillustrated embodiment, each LED fixture 22 is capable of generating3000 lumens, so that a total of 9000 lumens can be generated by thelighting fixture 10. Reflectors 24 are mounted to the sides of the LEDfixtures 22 opposite the heatsink base 14. The reflectors 24 function toreflect the light from the LED fixtures 22 toward an area that requiresillumination and can take many different forms depending upon thedesired lighting effect. An installation bracket 26 may be secured tothe heatsink base 14, as shown in FIG. 2, to enable the lighting fixtureto be secured to an appropriate supporting structure in a building. Amounting ring 28 may be mounted to the installation bracket 26 at aposition substantially aligned with lower end of the reflectors 24. Themounting ring 28 typically is used when most of the lighting fixture isconcealed behind a suspended ceiling and is not required for allembodiments. Additionally, the installation bracket 26 is only one ofmany different arrangements for securing the lighting fixture 10 in thebuilding.

A bridge 30 is mounted to a side of the heatsink 12 opposite the LEDfixtures 22 and a junction box 32 is mounted to a side of the bridge 30opposite the heatsink 12. An LED wire 34 extends to the junction box 32for delivering electrical power to the LED fixtures 22. A driver box 35is mounted in proximity to the lighting fixture 10 and is connected to apower cable 36. The driver box 35 converts the electric power into aform suitable for use by the LED fixtures 22.

Each foamed metal plate 16 in the illustrated embodiment issubstantially rectangular and has opposite top and bottom ends 38 and 40and opposite inner and outer edges 42 and 44. The bottom end 40 of eachfoamed metal plate 16 is bonded to the top surface 18 of the heatsinkbase 14. The top ends 38 of the foamed metal plates 16 define asubstantially planar array that supports the bridge 30 to which thejunction box 32 is mounted. The bridge 30 provides support for thefoamed metal plates 16 and maintains the substantially parallelrelationship between at least selected foamed metal plates 16 in thearray. The outer edges 44 of the foamed metal plates define asubstantially cylindrical locus with a diameter in the illustratedembodiment of approximately 7.50 inches. The foamed metal plates in theillustrated embodiment are arranged to define three arrays of parallelplates 16. The plates 16 in each array are offset from one another byapproximately 120° from the plates in the other arrays. The thickness ofeach plate 16 and the spacing between adjacent plates 16 is selected inaccordance with the heat dissipation requirements of the particularlighting fixture 10. In a typical embodiment, each fin 16 will be about0.20 inch thick and the spacing between adjacent fins 16 typically willexceed the thickness of each fin 16. The height of each fin 16 will varyfrom one installation to another. However, a height of approximately6.00-7.00 inch will be sufficient for most installations. The metal usedfor the heatsink 12 can vary from one installation to another. However,foamed aluminum has been found to provide desirable weight and heatdissipation characteristics, and therefore is preferred.

The embodiment of the invention illustrated in FIGS. 1-5 shows threearrays of parallel foamed metal plates 16. However, other arrangementsof foamed metal plates can be provided. For example, FIGS. 6 and 7 showa heat sink 12 a a single array of parallel fins 16 a. The arrangementof fins 16 a shown in FIGS. 6 and 7 provides very good air flow throughthe heatsink 12 a and hence provides very good heat dissipation.

What is claimed is:
 1. A lighting fixture, comprising: a heat sinkhaving a base with opposite top and bottom surfaces; at least one LEDlight fixture mounted to the bottom surface of the base; at least onefoamed metal plate having opposite first and second ends, the first endof the at least one foamed metal plate coupled to the top surface of thebase; a bridge coupled to the top surface of the at least one foamedmetal plate; and a junction box mounted on a surface of the bridgeopposite the heat sink.